From a Utah Mormon genealogy of more than one million individuals linked to a Cancer Registry of more than 30,000 cases, we will: (1) Determine the genetic contributions to the occurrence of cancer for specific sites in a general population, including the estimation of heritability for specific age-sex categories. (2) Fit specific genetic models which will best explain any observed patterns of the occurrence of specific cancer sites or groups found to cluster in large pedigrees. Components of the models will include modes of inheritance and factors which influence gene expression (such as age, sex, and pertinent environmental factors when known). In-depth pedigree and chromosomal marker studies provide important additional data for this analysis. (3) Inve tigate the potential association of a large number of immunologic, biochemical, and anthropomorphic genetic markers to various forms of cancer in an effort to characterize these traits for people who are at high genetic risk for acquiring the disease and then attempt to use this information for early detection or prevention of the cancer.